STUDIES ON IMMUNOPROPHYLAXIS OF FOWL CHOLERA

Abstract

The present study was successfully conducted in the Department of Veterinary Microbiology, University of Agriculture, Faisalabad. Twenty- one local isolates of P. multocida, isolated from natural outbreaks of fowl cholera were characterized. An excellent growth of P. multocida was obtained on dextrose starch agar having 5% chicken serum. Maximum isolates belonged to serotype 1 (47.62%), followed by serotype 3(28.57%), 4(14.29%) and 12(9.52%). All the serotypes were found virulent for chickens while no cross protection was observed among all the P. multocida serotypes. One plain and three adjuvanted inactivated fowl cholera vaccines were prepared from the locally isolated P. multocida serotypes (1, 3, 4 and 12) and their efficacy was evaluated and compared with a commercially available oil emulsified vaccine. It was evident from the results that double dose of oil emulsified (OEV-M) and alum adsorbed vaccines showed better and long lasting humoral antibody response and gave better (85-100%) protection against challenge as compared to plain (FIV), oil emulsified (OEV -V) and commercial oil emulsified (OEV -Com) vaccines. A 90-100% mortality was recorded in unvaccinated control. The IHA antibody titres were significantly low in case of birds vaccinated only once as compared to the birds received two doses of the vaccine. However, the best humoral immune response was recorded when the birds were primed with plain (FIV) vaccine and boostered either with oil emulsified (OEV -M) or alum adsorbed (AA V) vaccine. In field trials the birds primed with five and boostered either with OEV-M or AAV showed 85-100% protection against P. multocida serotypes 1,3,4 and 12 while the birds primed with FIV and boostered with OEV -Com gave 75-80% protection against challenge of P. multocida serotypes 1,3 and 4, but only 30% protection against serotype 12. Concludingly it was mentionable that this was for the first time in Pakistan that P. multocida isolated from natural outbreak of fowl cholera was serotyped and one plain and three adjuvanted vaccines were prepared in the country to develop immunity in chicken. The cost/dose of experimental plain (FIV) and adjuvanted vaccines (OEV-M, OEV-V and AAV) was calculated as Rupees 0.45 and 0.99 respectively and was less than 80% and 56%, respectively, of the cost of imported oil emulsified fowl cholera vaccines available in the market. Moreover, adjuvanted vaccines, OEV -M and AAV, proved much effective in protecting chickens not only in the controlled but also in the field conditions. So it is recommended that the' vaccines prepared from local isolates of P. multocida should be used in Pakistan to protect our poultry from fowl cholera and to save foreign exchange.